Metropolitan regions are set on top of a network of pipelines. Metal pipelines carry water supplies between the municipal water supply provider and the various houses and businesses. Concrete or metal pipelines transport sewage from those houses and businesses to the city's sewage treatment plant. Concrete or plastic pipes safely carry storm water collected by drains positioned along the edges of roadways to prevent flooding. These various pipelines typically have outside diameters between 42-110 inches.
Such pipelines need to be buried underground beneath obstacles on the property like buildings, roadways, parking lots, etc. Some pipelines can be installed simply by excavating a trench within the ground surface, laying the pipeline, and then filling the remainder of the trench with the excavated earth. However, other pipelines may need to be installed too far below the ground surface to make excavation with a steam shovel or trenching machine practical. Moreover, new water, sewer, or storm pipelines may need to be installed underneath obstacles like roadways, rivers, and other already existing pipelines where surface excavation would be impossible. For these types of deeper pipelines, underground boring of a tunnel dimensioned to accept the installed pipeline is the only option.
U.S. Pat. No. 2,656,683 discloses, for example, a method of installing pipes or ducts under, e.g., a lake or canal. Vertical shafts are dug on either side of the river or canal at the start and stop points for the pipeline. A tubular guide is then pushed into the earthen wall of the shaft at the proper depth and orientation for the pipeline. A pipe section is then inserted into the guide and pushed forward by means of a hydraulic jack. Subsequent pipe sections are connected to the end of each preceding pipe section and pushed into the earth by the hydraulic jack until the desired length of pipeline is installed.
However, many soil types or conditions, let alone rocks, will impede the efficient jacking of a pipeline in this manner. Thus, boring machines have been used within the industry to remove earth ahead of the pipeline that is being installed. U.S. Pat. No. 3,107,741 issued to Adams et al. discloses such a boring machine consisting of a hydraulic ram on tracks for pushing the pipe sections forward into the earth. A shaft bearing an auger along its length and a drill head at its distal end extends through the pipe sections and is rotated by the boring machine. The drill head excavates earth ahead of the leading edge of the pipe, and the auger flights convey this earth back through the pipeline sections to the trailing end where it can be removed. As each pipe section is pushed forward into the earth by the hydraulic boring jack, the jack is stopped and moved backwards on the track to provide space for another pipe section to be connected to the trailing end of the pipeline with the processes repeated for excavating earth with the drill head and pushing the pipeline forward.
U.S. Pat. No. 3,123,161 issued to Weber teaches a cog wheel-based rotary cutting head. Again, the frame for supporting this rotary cutting head is simply inserted into the pipeline, itself. U.S. Pat. No. 4,116,011 issued to Girault discloses a method for excavating pipeline tunnels in which the excavation cross-section cut by the drill head is larger than the cross-sectional area of the pipe section to make it easier to push the pipeline forward into the earth. In this case, no auger for moving the excavated earth backwards is used. Drilling mud is then injected under pressure into the annular region between the pipe exterior surface and tunnel wall to fill it and prevent misalignment of the pipeline.
Rotary drill heads are known within the industry for use in association with borer jacks. See, e.g., Adams, as well as U.S. Pat. No. 4,630,967 issued to Soltau; U.S. Pat. No. 3,767,836 issued to Geis et al.; U.S. Pat. No. 4,936,709 issued to Kimura; U.S. Pat. No. 5,749,678 issued to Dose et al.; and U.S. Pat. No. 5,846,027 issued to Fujii. Screw augers for transporting the excavated earth backwards through the pipe being installed are also known. See, e.g., U.S. Pat. No. 3,402,781 issued to Sandberg; and U.S. Pat. No. 3,174,562 issued to Stow. However, such boring machines/jacks using such rotary drill heads and screw augers, alone or in combination, appear to simply be inserted inside the pipe sections being installed. This arrangement creates several disadvantages. First, the rotary cutter or scraper heads can easily come into contact with the interior pipe surface, thereby making this conventional arrangement unsuitable for concrete pipe. Second, because the screw auger simply throws the excavated earth backwards inside the pipe, it is dangerous for workers using shovels to remove the earth in close proximity with the rotating flights of the screw auger. Third, this conventional arrangement for a boring machine/jack only works well for relatively small diameter pipe (Soltau, for instance, discloses the use of 12-16-inch diameter pipe for his boring machine/jack), and even more particularly, smooth surfaced pipe made of plastic or metal.
Another challenge for rotary boring machines is the need to properly guide them along the appropriate pipeline path over long distances. U.S. Pat. No. 3,917,010 issued to Fink addresses this issue by using a plurality of roller cutters on the head of the rotating screw auger inside the pipe that can be independently rotated to alter the direction of the cut tunnel. U.S. Pat. No. 3,945,443 issued to Barnes discloses an earth boring machine having an adjustable steering head with cutters and a plurality of wedge means that are arranged circumferentially around the front casing/pipe section to bear against the bored rock/earth surface. However, these steering mechanisms only provide for smaller steering corrections, and do not work well for larger pipe diameters.
U.S. Pat. No. 5,386,878 issued to Rowekamp adds an air hammer bit at the end of his rotary auger to try to enhance the cutting action, as well as compressed air to move the excavated earth and rock material backwards to the rotating auger flights for transport backwards in the pipe sections. But, a worker cannot stand inside or near the pipe safely while this earth and rock debris is moving backwards inside the same pipe. See also U.S. Pat. No. 5,125,768 issued to Ilomaki. U.S. Pat. No. 4,176,985 issued to Cherrington discloses a pipe casing installation method employing a transport fluid and positive pressure for moving the earth and rocks inside the pipe. U.S. Pat. No. 4,576,515 issued to Morimoto et al. uses a viscosity-imparting liquid to soften the soil ahead of the cutter head, as well as to carry the earth at the head of the boring device outside of it to fill the annulus between the excavated hole and the pipe. The structure of the Morimoto boring machine prevents the excavated earth from entering the machine, and therefore contains no transport screw auger.
It would be advantageous to provide an improved boring machine/jack for installing pipe sections containing a rotating cutter that does not come into contact with the interior surface of the pipe, a self-contained screw auger that efficiently transports the excavated earth without letting it fall inside the pipe sections, and a steering mechanism for maintaining proper alignment of the pipeline, as it is installed. Such a boring machine/jack could be used in association with larger diameter pipe, including concrete pipe having higher frictional interaction with the earth.